4 Questions to Ask About Tuberculin (TB Skin Test)

A TB test, also known as a Mantoux test or tuberculin skin test (TST), is a test that is used to determine if mycobacterium tuberculosis, the bacteria that causes TB, is present in your body. By placing a small amount of tuberculin under the skin, your doctor can assess the reaction to determine if you have TB. 

While blood tests can also be performed to determine if you have TB, TB skin tests are more commonly performed, especially in children under 5. However, while a TB skin test can show if you’ve ever been infected with TB bacteria, they can’t determine whether you have a dormant or active TB infection. For this, additional tests, such as a sputum test, will be required to see if you have an active case.

If you have a TB infection, the skin around your injection site will start to swell, harden, and/or change color. However, it’s the size of this bump, not the color, that will determine your results. This typically happens within 24-72 hours of the best being done, which is why it’s important to ensure you schedule a follow-up with your doctor within this time frame. 

Your attending doctor will measure the bump that forms along your forearm. If the measurement is less than 5mm, that’s indicative of a negative result. However, a measurement of more than 5mm is considered to be a positive result. If you test positive, further testing may need to be done to determine whether your case is active or latent. 

Tuberculosis is an airborne bacterial virus that is very contagious. TB can easily be passed along, especially in crowded environments. It is most commonly spread when someone with an active infection coughs or sneezes or projects their voice loudly, distributing tiny droplets containing TB germs into the air. When another person breathes in these droplets, the germs are then able to enter the lungs which leads to infection. 

Those that have a compromised immune system, such as those living with HIV/AIDS, are at a higher risk of catching TB compared to those with uncompromised immune systems. While there are antibiotics to treat TB, some forms of bacteria are immune which can make it more difficult to treat. 

TB skin tests are very common and are typically well tolerated by the general population. 

During the initial stage of testing, your doctor will inject a small amount of tuberculin, a sterile extract of the bacteria that causes TB, under the skin of your forearm. This will cause a small bump to form at the injection site within 24-78 hours. 

Between the 48-72 hour mark, your doctor will check the injection site and measure it. If the measurement is less than 5mm, that’s indicative of a negative result. However, a measurement of more than 5mm is considered to be a positive result. If you test positive, further testing may need to be done to determine whether your case is active or latent.

If you’ve been exposed to someone with TB, or are experiencing symptoms that you’re concerned about, connect with us at Immediate Care of Oklahoma. Our team of medical specialists will provide you with the safe, efficient, and painless testing you require to get the answers you’re looking for. For more information, contact us or schedule an appointment online. We have convenient locations to serve you in Oklahoma City, OK. We serve patients from West Moore OK, Norman (HealthPlex) OK, Norman (24th) OK, Edmond OK, Yukon OK, I-240 & Sooner RD OK, Tecumseh OK, Bethany OK, and surrounding areas.